The present invention is related to integrated circuits and, more particularly, to methods for placing an integrated circuit onto a substrate, such methods being tolerant of defects in the integrated circuit.
In the electronics industry, there exist various ways of mounting a semiconductor body containing an integrated circuit onto a substrate such as a circuit board. For instance, it is common to first package the semiconductor body as a xe2x80x9cchipxe2x80x9d, and then to attach the packaged chip to the substrate.
One common technique for fabricating a packaged chip involves placing the semiconductor body in contact with a redistribution layer, which rearranges the dense array of contact points on the semiconductor body in such a way that they are more easily accessible from the external world via a set of xe2x80x9cpinsxe2x80x9d. The electrical connection between the contact points of the redistribution layer and the contact points of the semiconductor body is commonly achieved by wire-bonding or flip-chip techniques. The pins are manufactured in such a way that they can easily engage with complementary contacts on the circuit board. Accordingly, connections between the pins of the packaged chip and the contacts on the circuit board can be achieved by way of bonding (soldering) or by providing releasable frictional connectors.
Typically, the substrate onto which the packaged chip is placed includes functional units that are designed to interact with functional units on the integrated circuit. Since each pin of the chip leads to a corresponding functional unit of the integrated circuit, and since each contact of the substrate leads to a corresponding functional unit of the substrate, there is conventionally only a single orientation in which the package can be placed vis-à-vis the substrate so that the desired interaction between the functional units is achieved.
However, during manufacture of an integrated circuit, the integrated circuit is formed may be affected by a defect. This defect may occur in a key region of the integrated circuit and thus it is possible that one or more of the functional units on the integrated circuit will be defective. As a result, the functional units of the substrate which are uniquely associated with the defective functional unit(s) of the integrated circuit prevent the desired overall functionality of the chip from being achieved. Under such circumstances, the chip becomes useless and needs to be discarded.
It should therefore be apparent that in a conventional chip-to-substrate assembly process, it may be necessary to go through several integrated chips until one with zero defective functional units is found, at which point the desired functionality of the chip can be realized upon assembly. A similar problem also arises in other manufacturing techniques whereby the semiconductor body is placed directly onto a circuit board. Clearly, procedures in which integrated circuits are discarded are extremely costly and wasteful, especially since the discarded integrated circuits may in actuality still contain multiple non-defective functional units.
It has been recognized that many types of integrated circuits, such as gate arrays, crossbars, memories, etc., contain multiple functional units that have a similar or an identical architecture. By xe2x80x9carchitecturexe2x80x9d of a functional unit is meant the physical arrangement of circuit elements associated with the functional unit. In some cases, full-mesh interconnectivity is provided amongst a set of the functional units, while in other cases, no connections are provided between any of the functional units. Additionally, in some instances, different functional units may assume different functional roles by virtue of being programmable. In any event, for many types of integrated circuits, different functional units are often interchangeable. The present invention exploits this interchangeability to provide a method of assembling a chip that results in less overall wastage of integrated circuits.
Specifically, a substrate is provided with a plurality of regions, at least one of which is operationally redundant. The integrated circuit is tested for defects and, if a functional unit is found to be defective, then the integrated circuit is oriented (e.g., rotated, translated or a combination of a translation and a rotation) with respect to the substrate such that the defective functional unit registers with the operationally redundant region of the substrate. A functional association is then formed between the remaining regions of the substrate and the non-defective functional units of the integrated circuit. Such functional association may be achieved by connecting each pair of unit and region. In this way, an integrated circuit with defective functional unit need not be discarded if the defective functional unit is made to register with the operationally redundant region of the substrate.
Therefore, the invention may be summarized according to a first broad aspect as a chip assembly, including a body of semiconductor material including an integrated circuit. The integrated circuit has a plurality of externally communicating functional units, at least one of which is defective. The chip assembly also includes a substrate on which the body of semiconductor material is mounted. The substrate has a plurality of regions, at least one of which is operationally redundant. The body of semiconductor material is positioned on the substrate such that each externally communicating functional unit other than the externally communicating functional unit that is defective is functionally associated with a respective one of the plurality of regions other than the region that is operationally redundant.
According to a second broad aspect, the present invention may be summarized as a combination of a body of semiconductor material and a substrate for receiving the body of semiconductor material. The body of semiconductor material has an integrated circuit having a plurality of externally communicating functional units, at least one of which is defective. The substrate has a plurality of regions, at least one of which is operationally redundant. The body of semiconductor material is capable of acquiring a first position and a second position on the substrate. In the first position, each externally communicating functional unit faces a first respective one of the plurality of regions, the externally communicating functional unit that is defective facing the region that is operationally redundant. In the second position, each externally communicating functional unit faces a second respective one of the plurality of regions, the externally communicating functional unit that is defective facing a region that is other than the region that is operationally redundant.
The present invention may be summarized according to a third broad aspect as a method of mounting a body of semiconductor material to a substrate. The method includes testing the integrated circuit for the presence of an externally communicating functional unit that is defective. If a defective externally communicating functional unit is found, the method further includes mounting the body of semiconductor material on the substrate such that the defective externally communicating functional unit registers with the region that is operationally redundant.
According to a fourth broad aspect, the invention may be summarized as a method of positioning a body of semiconductor material with respect to a substrate which includes testing the integrated circuit for the presence of a externally communicating functional unit that is defective and, if a defective externally communicating functional unit is found, orienting the body of semiconductor material on the substrate such that the defective externally communicating functional unit overlies the region that is operationally redundant.
The present invention may be summarized according to a fifth broad aspect as a method of positioning a body of semiconductor material with respect to a marker positioning device. The body of semiconductor material includes an integrated circuit having a plurality of externally communicating functional units. The method includes testing the integrated circuit for the presence of a externally communicating functional unit that is defective. The method further includes applying a marker to a surface of the semiconductor body. According to this fifth broad aspect, if a defective externally communicating functional unit is found, the body of semiconductor material needs to be oriented with respect to the marker positioning device prior to application of the marker in such a way that the marker, when applied, occupies a pre-determined orientation with respect to the defective externally communicating functional unit.
These and other aspects and features of the present invention will now become apparent to those of ordinary skill in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying drawings.